Contact terminal arrangement for electrical built-in switching unit

ABSTRACT

An electrical device ( 20 ), in particular an energy regulator or infinite switch, comprises a body portion ( 22 ) with one or more electrical elements ( 33,  D, B, C,  47 ) mounted thereto. The body portion ( 22 ) and the electrical element(s) ( 33,  D, B, C,  47 ) mounted thereto define an assembly having a minimum dimension which is termed the “thickness” of the assembly. At least one terminal ( 25, 57, 58, 59, 60, 61, 63 ) is also mounted to the body portion. The terminal has a mounting portion ( 27 ) and a contact portion ( 26 ) with the mounting portion ( 27 ) extending transversely to the thickness dimension to thereby result in a low-profile electrical device.

TECHNICAL FIELD

The present invention relates to terminal arrangements provided inelectrical devices. In particular, although not exclusively, theinvention relates to low profile control devices for electricalappliances such as hot plates in electric stoves. However, it will beappreciated that the use of such a device is not restricted to domesticappliances.

BACKGROUND ART

Control devices, commonly known as energy regulators or infiniteswitches are used primarily in domestic appliances where it is requiredto control heating of an element in an oven or a hot plate. The controldevices allow electricity through to the elements in pulses and it willbe appreciated that longer pulses will lead to higher elementtemperatures. The length of these pulses can be lengthened or shortenedby turning a knob on the control device so as to increase or decreasethe element temperature. The knob is attached to an actuator shaft whichis generally mounted perpendicular to a mounting plate which alsosupports a terminal housing. A number of electrical terminals areassembled into the terminal housing by sliding mounting portions of theterminals into slots in the housing extending in a directionperpendicular to the general plane of the mounting plate, i.e. parallelto the actuator shaft. (See FIG. 1) The terminals may be staked toretain them in position.

There are a number of disadvantages inherent in this type ofconstruction. Firstly, the construction requires the use of a separatemounting plate and housing. Secondly, the sliding of the terminalsperpendicularly to the mounting plate to assemble the control devicenecessitates an overall depth of the device which is greater than thelength of the terminals since the mounting portions of the terminalsextend into slots aligned with the lengthwise direction of theterminals. The staking of the terminals is also an additional assemblystep increasing the number of assembly operations.

It is therefore an object of the present invention to overcome at leastone of the abovementioned disadvantages or to provide the public with auseful choice.

DISCLOSURE OF INVENTION

In accordance with a first aspect of the present invention, there isprovided an electrical device including: a body portion; one or moreelectrical elements mounted to the body portion, the body portion andthe one or more electrical elements defining an assembly having athickness dimension which is the minimum external (or principal)dimension of the assembly; and at least one electrical terminal mountedto the body portion, the electrical terminal having a mounting portionand a contact portion, the mounting portion extending transversely tothe direction of the thickness dimension and being received in a recessextending from the side of the body portion, which side is substantiallyaligned with the thickness dimension, the mounting portion being adaptedfor sliding assembly into the recess.

Preferably, the mounting portion extends substantially perpendicular tothe direction of the thickness dimension. For example, the mountingportion may extend in either of the two orthogonal directionsperpendicular to the thickness dimension, parallel to the general planeof the body portion so as not to contribute to the overall thickness ofthe electrical device. The mounting portion may be a planar memberoriented such that the thickness dimension extends substantiallyperpendicular to the plane of the mounting portion. Further, it ispreferred that the contact portion of the electrical terminal has asubstantially planar contact surface which is substantially aligned withthe thickness dimension. In a most preferred form of the invention thecontact portion of the electrical terminals does not extendsubstantially beyond the thickness dimension. Thus, in the preferredform of the invention the terminal may be an L-shaped member whereby themounting portion and the contact portion define respective leg portionsof the L-shaped member.

Suitably, the terminal is disposed at or adjacent a side of the bodyportion which is substantially aligned with the thickness dimension. Aslot may be provided at the side of the body portion, the slot beingcomplementary in shape to the mounting portion of the terminal and themounting portion of the terminal being received in the slot.

Advantageously, a frictional fit is provided between the mountingportion of the terminal and the body portion. Alternatively, a snap fitis provided between the mounting portion of the terminal and the bodyportion.

Preferably, the body portion is substantially planar. In a preferredform of the invention, a plurality of terminals are provided and theelectrical element(s) and the terminals are mounted to extend from thesame face of the body portion. The device may further include a rotarycontrol actuator mounted to extend from the other face of the bodyportion in a direction substantially aligned with the thicknessdimension.

In a commercial embodiment of the invention, the body portion is of aone-piece plastic moulded construction.

In accordance with a second aspect of the present invention, there isprovided a control device for an electrical appliance, including atleast one electrical terminal and a substantially planar body portion,the electrical terminal being adapted for sliding assembly with the bodyportion in a direction substantially parallel to the plane of the bodyportion into a recess extending substantially parallel to the plane ofthe body portion.

By “substantially planar”, it is meant that the body portion extendslargely within a single plane with an average thickness dimensiontransverse to the plane being substantially less than the extent of thebody portion within the plane.

Suitably, there are a plurality of electrical terminals assembled inthis manner in the body portion. Each of the electrical terminals mayinclude a mounting portion extending substantially parallel to the planeof the body portion and a contact portion extending substantiallyperpendicular thereto. The recesses may be in the form of slots,apertures or recesses and desirably a frictional fit is obtained betweeneach electrical terminal and its respective receiving means.

In a preferred form of the invention, a control actuator is also mountedto the body portion with the control actuator having a longitudinal axisextending substantially perpendicular to the plane of the body portion.In a most preferred form of the invention, the body portion is in theform of a one piece moulded mounting plate with the receiving slotsintegrally formed in the mounting plate.

The control device may take the form of an energy regulator (infiniteswitch) incorporating a bimetallic switch and intended to be used in adomestic appliance. The body portion may be located behind a face plateprovided on the electrical appliance.

In accordance with a third aspect of the present invention, there isprovided a control device for an electrical appliance including at leastone electrical terminal and a control actuator having a longitudinalaxis wherein the electrical terminal is adapted for sliding assembly inthe control device in a direction substantially perpendicular to theaxis of the control actuator into a recess substantially perpendicularto the axis of the control actuator.

Preferably, a body portion is provided into which the electricalterminals may be slidably received during assembly. Suitably, thecontrol actuator may take the form of an actuator shaft to which anactuator knob can be fitted, the longitudinal axis of the actuator shaftdefining the longitudinal axis of the control actuator.

In order that the invention may be more readily understood, oneembodiment will now be described with reference to the drawings inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a typical energy regulator according to theprior art;

FIG. 2 is a side view of an energy regulator according to a preferredembodiment of the present invention;

FIG. 3 is a cross sectional view of detail of a terminal of the energyregulator shown in FIG. 2 is in unassembled configuration;

FIG. 4 is a detail similar to FIG. 3 except in assembled configuration;

FIG. 5 is a schematic diagram illustrating the operation of a bimetallicswitch incorporated into the energy regulator shown in FIG. 2, thebimetallic switch being shown in an operable position;

FIG. 6 is a schematic view, similar to that of FIG. 5 except with theswitch in the off position;

FIG. 7 schematically illustrates a control actuator for use inconnection with the bimetallic switch shown in FIGS. 5 and 6;

FIG. 8 is a side view of an energy regulator similar to that shown inFIG. 2, but with some slight variations;

FIG. 9 is an underside view of the energy regulator shown in FIG. 8;

FIG. 10 is a plan view of a spring member for use in the bimetallicswitch shown in FIG. 5;

FIG. 11 is a side view of the spring member shown in FIG. 10; and

FIG. 12 is a cross-sectional view through A—A of FIG. 10.

BEST MODE FOR CARRYING OUT THE INVENTION

In FIG. 1, the prior art energy regulator 10 is shown to comprise amounting plate 12 and a separate terminal housing 14. A controlactuator, including a control shaft 15 is mounted to the mounting plate12 and terminal housing 14. A number of electrical terminals 16 areshown which are staked or clipped in through slots in the housing 14,the slots extending perpendicularly to the plane of the mounting plate12. It can be seen that the provision of slots in the terminal housing14 which are aligned with the longitudinal direction of the electricalterminals 16 leads to excess bulk of the regulator 10, particularly inthe direction aligned with the axis of the control actuator 15.Typically, this dimension is 25 to 50 mm as shown in the figure.

FIG. 2 illustrates an energy regulator 20 according to the preferredembodiment of the present invention. The mounting plate and the terminalhousing are combined into a moulded plastic one piece body portion 22which is substantially planar apart from the boss for the mounting ofthe rotary control knob. The arrow indicates the general direction ofthe plane. With electrical elements mounted to one face of the bodyportion 22, it will be appreciated that the thickness direction liesalong any line perpendicular to this plane. A number of electricalterminals 25 are assembled with the one piece body portion 22 as shownin more detail in FIGS. 3 and 4.

Each of FIGS. 3 and 4 shows a partial section through the body portion22 and a section through one of the electrical terminals 25. It can beseen that the electrical terminal 25 comprises a first contact portion26 for making electrical contact with electrical components when theenergy regulator 20 is installed into an electrical appliance (notshown). The electrical terminal 25 also comprises a second mountingportion 27 extending transversely, in particular, at right angles to thefirst contact portion 26. The mounting portion 27 is received by acooperating receiving means 30 provided in one side of the body portion22. The receiving means 30 is in the form of an elongate slotsubstantially complimentary to the shape of the mounting portion 27. Inthe assembled configuration, it can be seen that the mounting portion 27and the receiving slot 30 extend in a direction substantially parallelto the general plane of the body portion 22, which is substantiallyperpendicular to the central longitudinal axis of the control actuator33 (See FIG. 2) and the thickness direction of the body portion. Thisconfiguration with all the terminals 25 having mounting portions 27extending substantially parallel to the plane of the body portion 22substantially reduces the bulk of the energy regulator in the directionperpendicular to the plane of the body portion 22.

The mounting portion 27 is slidably receivable in the mounting slot 30for easy assembly. A ramped projection 28 is provided on one face of themounting portion 27 for retention within a further recess 34 provided inthe body portion 22 to provide a snap fitting.

The energy regulator 20 is intended primarily for use in domesticappliances. The energy regulator 20 controls the heating of elements inovens or hot plates by allowing electricity to pass through to theelements in pulses. The energy regulator 20 also controls the length ofthe pulses so as to increase or decrease the element temperature.

The energy regulator 20 incorporates a bimetallic switch 40 (FIGS. 5 and6) to control the pulses of electricity between predetermined ones ofelectrical terminals 25. The bimetallic switch 40 is illustratedschematically in FIGS. 5 and 6.

The bimetallic switch 40 includes a bimetallic strip C anchored at oneend indicated by A. A ceramic heating element B is disposed on the topsurface of the bimetallic strip C. The bimetallic switch 40 alsoincludes a spring member D, the form of which is more clearly shown inFIGS. 10 to 12. As can be seen from FIG. 5, the spring member D isanchored at a first end F and a variable load is applied by thebimetallic strip at a second end 70 opposite to the anchored end. Thespring member D comprises a strip of spring metal with two spaced slots72 both extending from a central portion 74 of the spring strip 77towards the second end 70 but spaced from the second end. A transverseslot 75 connects the two parallel slots 72 to define an elongate contactportion 77 having a free end centrally disposed relative to the springstrip D. A first contact 79 is attached to the free end of the elongatecontact portion 77. The bimetallic switch 40 also includes a secondcontact E engagable with the first contact when the switch 40 is in theclosed position shown in FIG. 5.

It can be seen that the first end F has a longitudinal groove 81extending to the central portion 74 which it is believed, assists inestablishing residual stresses within the spring strip D. An additionalslot 83 is provided adjacent the first end F to stake the spring memberD to the Load Terminal 63 as will be discussed later in connection withFIGS. 8 and 9.

The bimetallic strip C can apply a varying load to the second end of thespring strip. The varying load will depend upon the heating of thebimetallic strip which determines the configuration of the bimetallicstrip as well as an initial bias applied by the control actuator 33, aportion of which is shown in FIG. 7.

The control actuator shaft 33 rotates a circular cam 45 which controlsthe location of a cam follower (calibration screw) 47 mounted to thebimetallic strip C.

The operation of the bimetallic switch will now be explained.

When the control actuator 33 is in the off position, the cam follower 47engages with the lowest point on the circular ramp 45 and little or nobias is applied to the bimetallic strip. The contacts to the heater Bare also open and thus little or no load is applied to the second end ofthe spring member D so that the first and second contacts are open asshown in FIG. 6. When the control actuator shaft 33 is rotated to anoperating position, the cam follower 47 is raised, thereby applying anupward bias to the bimetallic strip C, which in turn applies a load tothe second end of the spring member D to close the contacts as shown inFIG. 5. Electricity then flows through these contacts to the applianceelements. Electricity also flows through these contacts to the ceramicheater B which heats the bimetallic strip C which is configured to benddownwardly upon heating. This causes the contacts to open as shown inFIG. 6, whereupon current flow to the ceramic heater B and to theappliance element will cease and the bimetallic strip C will graduallycool to resume the configuration shown in FIG. 5, forcing the contactsto again close. This cycle of repeated opening and closing sendselectricity through to the appliance elements in pulses. By rotating thecontrol actuator 33 and increasing the upward bias on the bimetallicstrip C, it will be necessary to heat the ceramic heater B for a longerperiod of time to cause the necessary deflection in the bimetallic stripC. Thus, the length of the pulses through to the appliance elements willbe increased and the appliance elements will therefore be heated to ahigher temperature.

When the control actuator shaft 33 is rotated to the “full on” position,a lobe on the circular ramp increases the bias to such an extent thatthe bimetallic strip applies a sufficient load to the spring member sothat, irrespective of the deflection attained by the bimetallic strip,the contacts remain closed and the electricity flows continuously to theappliance elements.

As shown in FIG. 7, the circular ramp 45 also includes a lateral lobe 50to effect closing of an auxiliary switch to operate devices such aspilot lamps, extra elements, fans or safety circuits.

The cam follower 47 is provided in the form of an adjustment screw whichthreadingly engages in a portion of the bimetallic strip C to enablefine tuning adjustment to the pulse rate.

The bimetallic strip is configured into a U shape with one leg of the“U” forming the bimetal strip shown in FIGS. 5 and 6 and the other legof the “U” defining a heat compensating portion which is the portionmounting the cam follower 47 shown in FIG. 7. The heat compensatingportion acts as a compensator for when heat builds up within the energyregulator, ensuring that the pulses remain constant, irrespective ofheat build up. The configuration of the bimetallic strip C can be mostclearly seen in FIG. 9.

In connection with FIGS. 8 and 9, a detailed description of thecomponents of the energy regulator 20 will now be provided.

Up to this point, the numeral 25 has been used to collectively refer tothe electrical terminals. Each of the terminals will now be individuallyidentified in connection with FIGS. 8 and 9.

Component Description

Control Actuator (33)

The control actuator 33 includes a moulded thermoplastic shaft whichclips into and rotates in the body portion 22. Rotation of the shaftcontrols the switching mechanisms in the control device. It opens andcloses the separate circuits within the control device. It also adjuststhe output of the cycling mechanism by altering the attitude of theBimetallic Strip C by means of the Cam Ramp 45 on one end. Thiscomponent can have many forms to allow for many options of shaft sizeand switching operations. The shaft also provides part of the lockingmechanism between it and the body portion 22, for a “Push-to-Turn”option of control operation.

Body Portion (22)

All terminals slide and clip in from sides. The control actuator shaftclips into it. The mounting mechanism of the control shaft is anintegral part of the body portion 22. A protective terminal cover 55also clips onto the body portion 22. This component also provides thesecond part of the locking mechanism with the control shaft for a“Push-to-Turn” option as described above.

Terminal Cover (55)

Moulded thermoplastic cover. This clips onto the body portion 22 toprovide protection for the internal mechanisms of the control. It alsoincorporates a connecting strip from the neutral terminal to the ceramicheater.

Phase Terminal (57)

Pressed nickel plated steel terminal. This slides and clips into thebody portion 22 and provides for two external electrical connection bymeans of standard ¼″ terminals. It provides the connection to the springmember D for the main cycling mechanism of the control. This componentalso provides for connection to the on-off terminal 59 for a phase breakcircuit (fill current, used with contacts), or a pilot light circuit(low current, no contacts used). The terminal with the phase/pilotconnection can also be separated from the other terminal to provide anisolated circuit with the on-off terminals 59.

Neutral Break Terminal (58)

Pressed nickel plated steel terminal. This slides and clips into thebody portion 22 and provides for external electrical connection by meansof a standard ¼″ terminal. The blade part of this component is operatedby the control shaft. It switches the neutral or second phase circuitdepending on the application, between it and neutral terminal 61. Thiscomponent also provides the force required on the control shaft for a“Push-to-Turn” option.

On-Off Terminal (59)

Pressed phosphor bronze terminal. This slides and clips into the bodyportion 22 and provides for external electrical connection by means of astandard ¼″ terminal. The blade part of this component is operated bythe control shaft. It is used to switch a phase break circuit, pilotcircuit or isolated circuit as described above in connection with thephase terminal 57. This component also provides the detenting (indexing)of the control by operating in depressions on the surface of the controlshaft.

Divided Terminal (60)

Pressed phosphor bronze terminal. This slides and clips into theMounting Plate and provides for external electrical connection by meansof a standard ¼″ terminal. The blade part of this component is operatedby the control shaft. It switches to a connection on the Load Terminal63 to provide a circuit for a second load.

Neutral Terminal (61)

Pressed nickel plated steel terminal. This slides and clips into base 22and provides for two external electrical connections by means ofstandard ¼″ terminals. It provides the connection to the neural breakterminal 58 for the neutral or second phase circuit. It also providesfor contact to the neutral connector 64 to complete the neutral circuitwith the Ceramic Heater B.

Spring Member (D)

Pressed titanium copper spring. This component is permanently staked tothe load terminal 63 and completes the connection for the main cyclingmechanism between the phase terminal 57 and the load terminal 63. The“tongue” of the trident has a contact on it which completes this circuitwith the phase terminal 57. Self contained stresses put into thiscomponent when forming it provide the “snap action” for the switching ofthis circuit. The cycling of this circuit is controlled by the heatingand cooling of the Bimetallic strip B which moves the end of the springmember up and down, opening and closing the contacts.

Load Terminal (63)

Pressed nickel plated steel terminal. This slides and clips into thebody portion 22 and provides for two external electrical connections bymeans of standard ¼″ terminals. This component allows for the permanentstaked mounting of the spring member D and the hinged mounting of thebimetallic strip B. It is the second part of the cycling circuit betweenit and the phase terminal 57. It also provides a connection forswitching a second load circuit to the divided terminal 60.

Ceramic Heater (B)

Moulded alumina ceramic with resistive film and silver contacts screenedon to its surface. This component clips onto and is electricallyconnected to the bimetallic strip C at one end. It provides a connectionfor the neutral connector 64 at the other end to complete a heatercircuit between the load terminal 63 and the neutral terminal 61. Thiscomponent, when energized, provides the heat directly to the bimetallicstrip C to make the control cycle.

Bimetallic Strip (C)

Pressed bimetal. This component provides the clip mounting andelectrical connection for the ceramic heater B, the screw mounting forthe calibration screw 47, the hinge mounting of it to the load terminal63 and the switching (cycling) of the spring member D. Heat from theceramic heater 81 causes the bimetallic strip C to bend and relaxpressure on the spring member D which allows it to spring open and breakthe circuit. The bimetallic strip C then cools and eventually returns toits original position causing the spring member D to snap closed again,then the cycle repeats. The output of the control is altered by rotatingthe control actuator 33 which changes the attitude of the bimetallicstrip C.

Cam Follower (47) (Also Used as Calibration Screw)

Moulded thermoplastic screw. This component threads into the bimetallicstrip 12. The nose of the screw runs on a cam ramp surface of the end ofthe control actuator 33 to allow the output of the cycling mechanism tobe altered by the rotation of the control actuator. Adjustment of thescrew presets the output of the cycling mechanism at predeterminedsettings of the control actuator.

Neutral Connector (64)

Pressed stainless steel connector. This component fits into the terminalcover 55. It provides electrical connection between the ceramic heater Band the neutral terminal 61 to complete the heater circuit.

What is claimed is:
 1. An energy regulator for an appliance comprising:a body portion; one or more electrical elements mounted to the bodyportion, the body portion and at least one of said electrical elementsdefining an assembly having length, breadth, and thickness dimensions,the thickness dimension being the minimum external dimension of theassembly; a plurality of electrical terminals mounted in the bodyportion, at least one of said electrical terminals having a mountingportion and a contact portion, the mounting portion extendingtransversely to the direction of said thickness dimension and beingreceived in a recess formed in a side of the body portion, which side issubstantially parallel to the thickness dimension, the mounting portionbeing adapted for sliding assembly into the recess; wherein said contactportion extends substantially parallel to said thickness dimension anddoes not extend substantially beyond said thickness dimension.
 2. Theelectrical device of claim 1, wherein the mounting portion issubstantially planar and is oriented such that the thickness dimensionextends substantially perpendicular to the plane of the mountingportion.
 3. The electrical device of claim 1, wherein the contactportion of the electrical terminal has a substantially planar contactsurface which is substantially parallel with the thickness dimension. 4.The electrical device of claim 1 wherein the terminal is an L-shapedmember whereby the mounting portion and the contact portion definerespective leg portions of the L-shaped member.
 5. The electrical deviceof claim 1 wherein the contact portion is disposed for contact alongsidesaid side of the body portion.
 6. The electrical device of claim 1wherein the recess is in the form of a slot, which is complementary inshape to the mounting portion of the terminal.
 7. The electrical deviceof claim 1 wherein a frictional fit is provided between the mountingportion of the terminal and the body portion.
 8. The electrical deviceof claim 1 wherein a snap fit is provided between the mounting portionof the terminal and the body portion.
 9. The electrical device of claim1 wherein the body portion is substantially planar.
 10. The electricaldevice of claim 9 wherein a plurality of terminals are provided and theelectrical element(s) and the terminals are mounted to extend from thesame face of the body portion.
 11. The electrical device of claim 10further including a mechanical rotary control actuator mounted to extendfrom the other face of the body portion in a direction substantiallyparallel with the thickness dimension.
 12. The energy regulator of claim1 wherein the body portion is a unitary construction.
 13. The electricaldevice of claim 12 wherein the body portion is comprised of a plasticmolded construction.
 14. The energy regulator of claim 4 wherein thecontact portion is disposed for contact alongside said side of the bodyportion.
 15. The energy regulator of claim 4 wherein the recess is inthe form of a slot, which is complementary in shape to the mountingportion of the terminal.
 16. The energy regulator of claim 4 wherein africtional fit is provided between the mounting portion of the terminaland the body portion.
 17. The energy regulator of claim 4 wherein a snapfit is provided between the mounting portion of the terminal and thebody portion.
 18. The energy regulator of claim 4 wherein the bodyportion is substantially planar.
 19. The energy regulator of claim 4wherein the body portion is a unitary construction.
 20. The electricaldevice of claim 4 further including a mechanical rotary control actuatorextending from a face of the body portion in a direction substantiallyparallel with the thickness dimension.
 21. An energy regulator for anappliance comprising: a body portion, wherein said body portion issubstantially planar; one or more electrical elements mounted to oneface of said body portion; a rotary control actuator mounted to anotherface of said body portion, wherein the longitudinal axis of said rotaryactuator extends substantially transversely to the plane of said bodyportion; a plurality of electrical terminals mounted in the body portionfree from mechanical contact with make/break contacts, each of saidelectrical terminals having a mounting portion and a contact portion,the mounting portion extending substantially transversely to thelongitudinal axis of said rotary actuator and being received in a recessformed in a side of the body portion, said side being substantiallyparallel to the longitudinal axis of said rotary actuator, said mountingportion being adapted for slidable receipt into said recess; saidcontact portion extending substantially parallel to the longitudinalaxis of said rotary actuator; and said one or more electrical elementand said plurality of terminals extending from the same face of saidbody portion.
 22. A method for fabricating an energy regulator for anappliance, said method comprising: providing an assembly having length,breadth, and thickness dimensions, the thickness dimension being theminimum external dimension of said assembly, said assembly including oneor more electrical elements mounted to a body portion, said body portionincluding a plurality of recesses formed in at least one side thereof,said side being substantially parallel to the thickness dimension;providing a plurality of electrical terminals, each of said terminalsincluding a contact portion and a mounting portion; selectivelyinserting each of said terminals into each of said recesses, saidmounting portion extending transversely to the thickness dimension, saidcontact portion being substantially parallel to the thickness dimensionand not extending beyond the thickness dimension.